1
977
4
.0 with isobutyl- and propionaldehydes, respectively. The amino group with bulkier
dibenzyl (lb) gives larger ratios (32, 10 and 9 in the same order), p-Anisaldehyde
gives very low (0.5~1.5) selectivity with both anions, lb and lc.12,13) Enolizable
ketcnes (e.g. cyciohexanone) give the pretonation product, 1-alkylpyrrolidine,
lowering the yield of 3. Halogenoalkyls afford alkylation products and bis(1-
pyrrolidinyl)alkanes resulted frcm single electron transfer and subsequent radical
coupling.
Trialkyltin chlorides yield the corresponding aminostannanes.
Thus, the present study disclosed a convenient method of generation of "non-
stabilized" c~-aminocarbanions, their thermal stability, and reactions with some
electrophiles. Since the "stannane route" is not applicable to the generation of
secondary carbanions, 14) the method may be useful in diastereoselective synthesis
of 2-aminoalcohols.
REFERENCES AND NOTES
1
2
) Present address; Faculty of Pharmaceutical Sciences, Tokushima Bunri University,
Tckushima 770, Japan.
) The "stabilized" c~-aminocarbanions are defined as those with a stabilizing group
on the anionic carbon (e.g. ~-system) or on the nitrogen (e.g. acyl group). (cf. D.
Seebach, I. M. P. Huber, and M. A. Syfrig, Helv. Chem. Acta, 70, 1357 (1987), A.
I. Meyers, D. B. Miller, and F. H. White, J. Am. Chem. Soc., 110, 4778 (1988), and P.
Beak and W.-K. Lee, Tetrahedron Lett., 30, 1197 (1989)). ~-Aminocarbanions only
with alkyl or aralkyl group are consequently "non-stabilized".
3
4
)
)
References on the carbanions stabilized by the 2nd-row elements are numerous.
For reviews, e.g.W.-K. Li, R.H. Nobes, D. Poppinger, and L. Radom in Comprehensive
Carbanion Chemistry, Part C. E. Buncel and T. Durst ed., Elsevier, 1987, p25.
For the "non-stabilized" carbanions with c~-oxygen, see J.S. Sawyer, A. Kucerovy,
T.L. Macdonald, and G.J. McGarvey, J. Am. Chem. Soc., 110, 842 (1988) and the
references cited therein.
5
6
) a. D.J. Peterson, J. OrganometaL Chem., 21, p63 (1970). b. Idem, J. Am. Chem.
Soc., 93, 4027 (1971).
)
The "stabilized" ~-aminocarbanions are well known and utilized in organic
syntheses. For reviews, see a. P. Beak, W.J. Zajdel, and D.B. Reitz, Chem. Rev., 84,
471 (1984). b.A. Kfief, Tetrahedron, 36, 2531 (1980). c. D. J. Peterson,
OrganometaL Chem. Rev., A, 7, 295 (1972).
7
8
) Cohen et al. have successfully applied a radical anion to generate "non-stabilized"
c~-oxycarbanions from ~-aikoxy-sulfide. T. Cohen and J.R. Matz, J. Am. Chem. Soc.,
1
02, 6900 (1980). T. Cohen and M~-T. Lin, ibid., 106, 1130 (1984).
)
P.K. Freeman and L.L. Hutchinson, J. Org. Chem., 46, 1924 (1980).